1. Field of the Invention
The present invention relates to a device for the display of engravement shape of an eyeglass lens and a method and apparatus for machining a peripheral edge of the lens using the display device.
2. Description of the Related Art
According to the prior art, in a lens grinder (a lens peripheral edge machining apparatus), an eyeglass lens for the right-hand eye is subjected to grinding in accordance with a lens peripheral shape of one (right-hand eye) eyeglass frame portion and thereafter an eyeglass lens for the left-hand eye is subjected to grinding in accordance with a lens peripheral shape of the other (left-hand eye) eyeglass frame portion. A certain lens grinder of this type is provided with a display device which displays engravement information by engravement simulation before grinding so that right and left eyeglass lenses can be fitted tastefully into the eyeglass frame. In such a lens grinder, an estimated engravement shape after the machining is displayed on the display device by engravement simulation, the worker for the machining is allowed to recognize at which position from a front end of an eyeglass lens on the lens edge face a vertex position between engravements after the grinding work is formed, and thereafter eyeglass lenses for the right and left eyes are subjected to grinding.
As eyeglass lenses, various lenses are available, including plastic lenses, flat lenses, and minus lenses. In the conventional lens peripheral edge machining apparatus, for the purpose of fitting eyeglass lenses into an eyeglass frame tastefully, a division ratio, which is defined in terms of a ratio between the distance from a front end of each lens on the lens edge face up to a vertex position between engravements and the distance from the vertex position between engravements to a rear end of the lens, is set, for example, at 4:6 in case of a plus lens, 5:5 in case of a flat lens, and 3:7 in case of a minus lens, and engravement is subjected to grinding in this condition.
On the other hand, a certain eyeglasses wearer wears eyeglass lenses which are markedly different in their degrees between the right and left eyes. For example, a certain eyeglasses wearer wears a plus lens for the right-hand eye and a minus lens for the left-hand eye. If a plus lens is subjected to grinding and engravement is formed at a division ratio established for the plus lens, while if a minus lens is subjected to grinding and engravement is formed at a division ratio established for the minus lens, and when eyeglass lenses for the right and left eyes are fitted in right and left lens frame portions, respectively, of an eyeglass frame, one eyeglass lens looks protruding too much from the front side of the lens frame in comparison with the other eyeglass lens, that is, both lenses do not look protruding uniformly from the lens frame front side, thus giving rise to the problem that the eyeglasses when put on its wearer look poor.